This invention relates generally to conveying systems having plural power-driven conveying sections and, more particularly, to apparatus for varying the effective length of the system by controlling the diversion of conveyed articles from one conveyor section to another.
Many conveyor applications require that articles transported on one conveyor belt be transferred to another conveyor belt that may be traveling in another direction, such as the opposite direction. Stationary rails spanning the conveying surfaces of the belts at a transfer point are often used for this purpose. In some applications, such as article accumulation, the transfer point can be moved. The moving transfer point allows the effective length of the conveying path and, consequently, the amount of articles accumulated to be controlled. In a spiral accumulator, such as that shown in U.S. Pat. No. 6,152,291, two parallel conveyor beltsxe2x80x94an infeed belt and outfeed beltxe2x80x94are helically arranged with a rotatable transfer mechanism traveling between them. The position of the transfer mechanism depends on the relative speeds of the two oppositely-moving belts. A guide plate on the transfer mechanism directs articles from the infeed conveyor belt to the outfeed belt. A rotatable member in the transfer mechanism simultaneously engages drivers formed on the specially designed infeed and outfeed belts. The rotatable member, driven by the drivers, translates the transfer mechanism and its attached guide plate along the belts as determined by their relative speeds. The rotatable member rides along with the transfer mechanism.
A more common accumulation system is known as a bi-di (bi-directional) table. Typically, a bi-di table includes a bi-directional conveyor belt arranged to run perpendicular to a main conveyor belt. As articles build up on the main conveyor belt, backpressure directs them onto the bi-di belt, which runs in a direction away from the main conveyor. In this way, articles are accumulated on the bi-di belt""s surface. As downstream processes require more articles, the direction of the bi-di belt is reversed so that the accumulated articles are pushed back onto the main conveyor belt. These bi-di tables, which support the bi-di belt and its drive mechanisms, are generally rectangular in shape with drive or idler shafts for sprockets or pulleys at each end. But, unlike the spiral accumulator, these simple, ubiquitous tables are not first-in, first out.
Thus, there is a particular need for a simple first in, first-out accumulation system, especially one that can be easily retrofitted in a bi-di table. More generally, there is also a need for a simple mechanism for diverting articles from one conveyor belt to another, such as oppositely-moving conveyor belts.
These needs and others are satisfied by a novel article-diverting apparatus embodying features of the invention. In the apparatus, a first conveyor belt is driven in a first direction at a first speed. A second conveyor belt is driven at a second speed in a different second direction, typically the opposite direction. A stream of articles is conveyed along a conveying surface of the first conveyor. A carrier travels along a path generally parallel to the first and second conveyor belts. A diverter element affixed to the carrier extends across at least a portion of the conveying surfaces of the first and second belts to divert articles in the stream from the first belt to the second belt. The carrier is controlled by a differential drive mechanism at a speed that depends on the speeds of the first and second conveyor belts. In this way, the position of the diverter element and, hence, the transfer point are determined by the relative speeds of the two belts.
In one version of the apparatus, the differential drive mechanism is stationarily attached to a framework supporting the carrier and the first and second belts. In another version, the differential drive mechanism is attached, not directly to the first and second belts, but to a first drive mechanism driving the first belt and to a second drive mechanism driving the second belt. This permits non-custom, less-expensive, standard belts to be used as the first and second belts.
In a first-in, first-out accumulator using the apparatus of the invention, a stream of articles at an upstream position on a main conveyor is supplied to the first, or infeed, conveyor belt, transferred to the second, or outfeed, conveyor belt by the diverter element on a carrier, and then fed by the second belt back to the main conveyor line at a downstream location. The amount of accumulation is determined by the carrier drive mechanism, which positions the carrier and diverter element along the infeed and outfeed belts depending on their relative speeds.
In other versions, the carrier is an endless carrier belt parallel to the first and second belts. The belt can be an intermediate belt between and abutting the first and second belts with a transfer surface portion across which products are transferred from the first belt to the second belt. Alternatively, the carrier belt flanks the first conveyor belt and carries the affixed diverter element. The flanking belt can be used in conjunction with another flanking belt on the opposite side of the second conveyor that provides twosided support for the diverter element. In this version, the first and second conveyor belts can be abutted for direct transfer of articles from one to the other. In one version in which a carrier belt is used, the first and second belts engage rotating elements including aligned shafts with sprockets about which the belts articulate. The differential drive mechanism is rotationally coupled to the rotating assemblies and engages the carrier belt to drive at a speed that depends on the relative speeds of the conveyor belts. This version is especially easy to retrofit in an existing bi-di table to achieve first-in, first-out capability.
In one version, the differential drive mechanism is differentially geared to the first and second drive mechanisms. But the belts and carrier can alternatively be controlled by a controller that individually controls the drive mechanisms of the first and second conveyor belts and the carrier. In either of these examples, the drive characteristics can be tailored for various applications by setting the speed of the carrier to be as1xe2x88x92bs2, where s1 is the speed of the first conveyor belt, s2 is the speed of the second conveyor belt, and a and b are adjustable parameters that are chosen to fit the application.
Thus, the apparatus provides clear advantages in diverting articles from one conveyor belt to a parallel, oppositely moving conveyor belt.